1. Field of the Invention
The present invention relates to electrophotographic photosensitive members, process cartridges and electrophotographic apparatuses. In particular, the present invention relates to an electrophotographic photosensitive member, a process cartridge and electrophotographic apparatus provided with a photosensitive layer containing a specified resin and charge transfer material.
2. Description of the Related Art
Recently, various electrophotographic photosensitive members containing organic photoconductive materials have been intensively developed. For example, U.S. Pat. No. 3,837,851 discloses a photosensitive member having a charge transfer layer containing triallylpyrazoline, and U.S. Pat. No. 3,871,880 discloses a photosensitive member comprising a charge generating layer containing a perylene pigment derivative and a charge transfer layer containing a condensation product of 3-propylene and formaldehyde.
Organic photoconductive materials are sensitive to their characteristic wavelength ranges. For example, Japanese Unexamined Patent Publication Nos. 61-272754 and 56-167759 disclose compounds highly sensitive to visible light, and Japanese Unexamined Patent Publication Nos. 57-195767 and 61-228453 disclose compounds highly sensitive to an infrared region. Among them, compounds highly sensitive to an infrared region have been increasingly used in laser beam printers (hereinafter referred to as LBP) and LED printers.
Meanwhile, electrophotographic photosensitive members must be provided with sensitivity, electrical characteristics, mechanical properties and optical characteristics suitable for the electrophotographic processes employed. In particular, electrophotographic photosensitive members must be durable against repeated electrical and mechanical forces, such as charging, exposure, development, transfer and cleaning, directly applied to their surfaces. In particular, they must have high electric and mechanical resistance to deterioration due to ozone and nitrogen oxides forming during charging, and surface abrasion occurring during discharging and cleaning.
Another problem to be solved is a phenomenon called "photomemory" in which a residual carrier on the light irradiated section forms a potential difference with the nonlight irradiated section.
Contact charging processes, in which a charging member comes in contact with an electrophotographic photosensitive member and the electrophotographic photosensitive member is charged by applying a voltage to the charging member, have been increasingly employed, as disclosed in Japanese Unexamined Patent Publication Nos. 57-178267 and 58-40566, and cause new problems. Contact charging processes have some technical and economical advantages as compared to scorotrons; for example, extremely low ozone formation, and low electricity consumption (in scorotrons, approximately 80% of current applied to a wire of the charger flows to a shield of the charger).
However, contact of the charging member with an electrophotographic photosensitive member requires a higher mechanical strength for the electrophotographic photosensitive member. Further, use of an input voltage, in which an AC voltage is superposed on a DC voltage, is proposed in order to improve charging stability of the contact charging processes due to electric discharge (Japanese Unexamined Patent Publication No. 63-149668).
Superposition of an AC voltage drastically increases the current flow in the electrophotographic photosensitive member concurrently with improvement in charging stability, and thus causes increased damage or abrasion of the electrophotographic photosensitive member. Therefore, electrical durability, as well as mechanical strength, are required for electrophotographic photosensitive members.
Also, high resistance to solvent cracks formed by adhesion of mechanical oil and finger grease are essential for electrophotographic photosensitive members.